This was originally published on Native Plants & Wildlife Gardens.
Planning a garden on a balcony is often a challenging prospect, but using native plants can both help, and cause further frustration. Balconies are a very different environment from the places native plants usually grow. In addition to the usual challenges of balcony gardens such as using containers, reflected heat and sun exposure, the weather in cities where most balconies are located is also different. The humidity is often lower in the city, precipitation is higher due to a lack of tree canopy and there’s more runoff. Temperatures in the city are also higher due to the urban heat island effect and in addition, the sun often reflects off the buildings and projects more heat onto balconies. Air quality is another factor to consider as well as the wind, which is often a huge factor for balconies, particularly those a couple floors or higher. Plants transpire more when it’s windy and require more water as a result.
Due to these challenges, plant choice is a very difficult process. A lot of it is trial and error as I’m finding on my balcony. I live on the sixth floor of a building on top of a hill with major bodies of water within a couple miles to the west and east. My balcony faces southwest and is situated between two large pillars creating a complex dynamic of sun and shade. Coupled with a large sliding glass door that reflects the sun, it’s an interesting place to grow plants. Fortunately for me, because my balcony has several different ‘zones’, when a plant starts looking bad, I can simply move it to another spot to see if it does better. Being up on top of the hill the wind takes a huge toll on my plants, especially during the winter and early spring. My Vine Maple (Acer circinatum) has leaf damage due to the constant rubbing against the building wall from the wind. My Oregon-grape (Mahonia nervosa) is mostly dead because it does very poorly in the wind.
I’m trying to create some windbreak with vines, but they grow very slowly. Another option that creates a good windbreak is bamboo. The benefit of a balcony is that even though most gardeners would denounce the use of bamboo faster than I could blink, I could use bamboo because there’s no risk of it spreading by root to the neighbors thanks to growing in containers.
Another problem I face is the construction of the floor of the balcony which is metal slats, it’s not solid. Why does this matter? Two reasons, the first is that the wind comes up through the bottom in addition to the sides. I solved this problem by putting down an outdoor rug and then some wood decking over that. The second reason is that it’s quite a problem when I water the plants for all of the apartments below me. The solution is to put containers which have drainage holes into containers that don’t have holes with a layer of rocks or gravel. The problem with this is that the plants stand in water when it rains heavily. I’ve had to learn to balance leaving the plants out of their undraining pots during the winter when it rains a lot and put them in during the summer when there’s less chance of a downpour. During the spring and fall it’s a constant dance moving them in and out. The result is that my plants have to be able to stand some shifting around and temporary standing water. Half of my balcony gets more rain than the other half and that’s where I try to put the plants that like or tolerate water like the Mertens’ Sedge (Carex mertensii). It’s all very complicated.
When I first started buying plants for my balcony I bought any native plant I could find. My experience has changed that attitude however, now I try to research native plants before buying them. Many of our native plants grow in forests, like the Oregon-grape, and therefore are intolerant of the wind and would not make good choices for a balcony. On the other hand, we also have many native plants that grow on sides of hills and other tough locations such as Kinnikinnick (Arctostaphylos uva-ursi), which fares well on my balcony. Sword Fern (Polystichum munitum) is another that has done well and creates a dense mound which insects will shelter in. My Wood Sorrel (Oxalis oregana) also does very well placed in a location that only gets late afternoon sun. The trick is to think about where the plants are found in the wild and if they grow where there is high wind, tough soil conditions or low nutrients, they’ll probably do well on a balcony. Many others will do well but will require a little more attention.
Other growing aspects of native plants to consider are the roots. Plants that grow roots which are shallow, many of those that grow on rock outcrops for example, will do well in containers. Watering may be necessary even with native plants that are drought resistant because they are growing in containers and can’t develop the deep roots to tap from the soil water. Fertilizing is also necessary because balcony plants won’t get all the leaf and other debris on the soil. Survival over winter is another concern for even native plants in containers because while they may survive fine in the ground, containers on the 10th floor is another matter.
Lastly is the problem of pests. Amazingly to me, my plants are plagued with aphids just like anywhere else. How they manage to find plants six floors up is beyond me, but they do. If you look up how to get rid of aphids, most resources say to simply blast them off with a hose. That is certainly not an option on most balconies so it’s more difficult to manage certain pests. I try to encourage predators such as lady beetles to combat them and sometimes I squish them myself when they get to be a big problem. I do like having some because it provides a source of food for my insect visitors. Read about the lady beetle family that grew up on my balcony: The Life of the Lady Beetle. The bonus on the other hand, is that being up above ground level, I do avoid other pests and problems.
Balcony gardening is possible for nearly every size and shape they come in. It’s possible to also attract great wildlife on balconies. I’ve had several species of lady beetles, other beetles, spiders, wasps, hoverflies and other interesting species of flies, bees and hummingbirds. It challenges you to be creative and it provides an opportunity to be very intimate with the plants and everything that makes use of them.